Method and apparatus for sequential plasma treatment

ABSTRACT

The apparatus for plasma treatment of a non-conductive hollow substrate ( 1 ), comprises a plurality of ionisation energy sources ( 7 - 10 ) disposed adjacent to each other all along the part of the substrate to be treated. The apparatus further comprises a processing means ( 11 ) for sequentially powering the plurality of ionisation energy sources from a radio frequency power source ( 6 ). Each ionisation energy source ( 7 ) is comprised of two parts ( 7   a   , 7   b ) sandwiching the substrate. The ionisation energy sources can be capacitively or inductively coupled plasma sources.

FIELD OF THE INVENTION

[0001] The present invention relates to a method and an apparatus forsubstrate treatments using plasma such as, for example, polymertreatment for biomedical devices or food and pharmaceutical packagingdevices. In particular, the present invention relates to plasmatreatment or deposition in non conductive hollow substrates having largeaspect ratio such as small diameter tubes, flat boxes.

BACKGROUND OF THE INVENTION

[0002] Hollow substrates with a large aspect ratio are commonly used invarious technological fields such as catheters or endoscopes for medicalmaterials and packaging for food or pharmaceutical applications. Theexpression “large aspect ratio” means that the hollow substrate has atleast one dimension that is much larger than another one, and moreparticularly that the length of the substrate is much larger than adimension of the substrate aperture. FIG. 4 shows two examples of hollowsubstrates which have a large aspect ratio L/a, where L is the length ofthe substrate and a is the smallest dimension of the substrate aperture.A tube 1 comprises an inner cavity having a large length L with respectto the diameter a of the tube. Large aspect ratio substrates may alsohave a form of a flat box 101 which exhibits a little aperture height ain comparison with its length L.

[0003] A general difficulty of the use of plasma treatment is thecomplexity to treat internal walls of such substrates. Indeed, plasmatreatment of this kind of substrate is difficult to perform since theplasma creation into large aspect ratio hollow substrates generallypresents a lack of plasma uniformity and thus of treatment. A uniformtreatment is ensured only if, for the whole substrate length, the gasprecursor concentration, the local plasma density and the pressure arerigorously constant.

[0004] The creation of the plasma inside the substrate is carried out byapplying electrical energy to the process gas. The electrons areaccelerated by an electric field and ions are created from inelasticcollisions between gas molecules and the accelerated electrons. Theelectrical energy to accelerate electrons in the gas is generallyperformed by a varying electric field, a varying magnetic field, orboth.

[0005] Two main problems occur when the aim is to treat or to depositplasma along a hollow substrate. The first problem concerns thedifficulty to create a uniform plasma density along the substratelength. Indeed, to achieve this condition, a constant electrical energymust be applied to the substrate, which becomes less feasible over acertain size.

[0006] The second problem is that uniformity of treatment along thewhole length can be ensured only if a constant quantity of precursorreacts all along the substrate length. Even if a special energy sourcearrangement can be implemented to create uniform plasma density alongthe substrate length, the precursor concentration will decreaseirremediably as soon as the gas precursor has flowed the substrate,since higher precursor consumption will occur at the substrate gasinlet.

[0007] To remedy this problem, several solutions have been developed.One of them, described in U.S. Pat. No. 4,692,347 and illustrated inFIG. 5, consists of shifting a tube 502 to be treated with respect to afixed plasma source 505 in a vacuum chamber 501. The tube 502 to becoated is initially wound on a reel 508 with an extremity incommunication with a monomer source 503 via a flow controller 504. Theplasma is created inside the tube 502 by continuously passing the tubein a glow discharge zone formed by the fixed reactance coupling source505 formed from two electrodes radio frequency powered. The tube partwhose interior wall has been coated is wound on a receiving reel 509. Alow absolute pressure is maintained inside the tube by evacuating means506 and 507 connected to the other extremity of the tube.

[0008] However, such a solution has drawbacks. To roll and unroll thintubes of low or high stiffness can lead to local shrinking or folding,that is to say irreversible tube deformations. Moreover, the structureand implementation of the evacuating means are complex and it isdifficult to guarantee a good pressure control along the tube. Thesedifficulties affect not only the reliability of the plasma treatment ofa tube but also the costs and the rapidity of the treatment.

[0009] Conversely, another solution is to attach the plasma source to amotion mechanism for shifting the plasma source with respect to the tubeto be treated. However, such a mechanism is complex and does not permitto control the parameters for a plasma uniform treatment in thesubstrate. The velocity and the precision of the plasma source motionrequired for uniform plasma treatment leads to develop electroniccontrol system sensibly increasing the cost of the treatment. Moreover,such a device is limited to single tube treatment.

OBJECT AND SUMMARY OF THE INVENTION

[0010] In view of such aspects, an object of the present invention is toprovide a method and an apparatus in which the above-mentioned problemscan be solved. In other words, an object is to provide a method and anapparatus which allow a plasma treatment of hollow substrates in uniformway all-over the inside parts of the substrates.

[0011] To this end, there is provided a method for plasma treatment of ahollow substrate, characterised by comprising the steps of placing aplurality of ionisation energy sources all along the part of thesubstrate to be treated, injecting a process gas inside the substrate,the gas containing a precursor for plasma creation, maintaining apressure inside the tube within a predetermined range, and powering theplurality of ionisation energy sources, in sequence, for selectivelycreating plasma inside the substrate at a location corresponding to therespective source powered, the step of injecting the process gas isrepeated at least before the powering of each ionisation energy source.

[0012] Thus according to the present invention, uniform plasma densitycan be created along the substrate while having a constant gasconcentration reacting along the tube.

[0013] According to an aspect of the present invention, the plurality ofionisation energy sources are either capacitively coupled plasma sourcesor inductively coupled plasma sources.

[0014] The plurality of ionisation energy sources may be powered by acommon radio frequency power source or by a separate radio frequencypower source for each ionisation energy sources.

[0015] According to another aspect of the invention, the ionisationenergy sources are powered in a pulsed fashion.

[0016] The step of injecting a process gas inside the substrate can bealso performed in a pulsed fashion. Although the process gas can bepulsed without using a pulsed ionisation energy source and conversely,according to an aspect of the present invention, the gas flow can bepulsed in accordance with the sequences of powering the ionisationenergy sources. This ensures that the process gas and therefore theprecursor, is renewed in front of the ionisation energy sources betweeneach powering sequence. The precursor consumed after a sequence ofpowering is replaced so as to maintain a constant precursorconcentration each time the plasma is created in the substrate.

[0017] According to another aspect of the invention, the process gas ispermanently flowed in the substrate at a constant precursor rate.Therefore, in this case, the step of injecting the process gas insidethe substrate is continuously performed during the entire plasmatreatment of the substrate.

[0018] More precisely, the substrate is a hollow substrate with a largeaspect ratio.

[0019] In an embodiment, the plurality of ionisation energy sources(107-112) are placed according to an array of two dimensions.

[0020] The present invention also provides an apparatus for plasmatreatment of a non-conductive hollow substrate, comprising generationmeans for generating a plasma in the substrate, characterised in thatthe generation means comprise a plurality of ionisation energy sourcesdisposed adjacent to each other all along the part of the substrate tobe treated and in that said apparatus further comprises a processingmeans for sequentially powering the plurality of ionisation energysources from radio frequency power supply means.

[0021] More specifically, the radio frequency power supply meanscomprise a single radio frequency power source for powering theplurality of ionisation energy sources or a plurality of separate radiofrequency power sources for respectively powering the plurality ofionisation energy sources.

[0022] According to an aspect of the invention, the radio frequencypower supply means is of a pulse generator type for powering theionisation energy sources in a pulsed fashion. The apparatus of thepresent invention may also comprise a gas flow controller forcontrolling the kinetic of the process gas flowing into the substrate.The gas flow controller may also serve for injecting the process gas ina pulsed fashion. Although the process gas can be pulsed without using apulsed ionisation energy source, according to an aspect of theinvention, the gas flow controller can be connected to output means ofthe processing means in order to command the gas flow in accordance withthe sequences of powering the ionisation energy sources. This ensuresthat the process gas and therefore the precursor is renewed in front ofthe ionisation energy sources between each powering sequence. Theprecursor consumed after a sequence of powering is replaced so as tomaintain a constant precursor concentration each time the plasma iscreated in the substrate.

[0023] The plurality of ionisation energy sources may be capacitivelycoupled plasma sources or inductively coupled plasma sources.

[0024] Specifically, each ionisation energy source compriseselectromagnetic means for producing through the substrate a magneticflux perpendicular to a direction of a substrate length.

[0025] According to an embodiment of the invention, the apparatusfurther comprises a plasma chamber provided with two oppositely facingfield admission windows and, as electromagnetic means, first and secondopposite coil arrangements located on an outer surface of the first andsecond windows respectively, the first and second coil arrangementsbeing connected to power supply line such that a current of a samedirection flows simultaneously in the first and second coilarrangements.

[0026] The first and second coil arrangements comprises each an inductorhaving a serpentine form.

[0027] Advantageously, the first and second coil arrangements furthercomprises a magnetic core associated with the inductors of the coilarrangements, the magnetic core presenting a pole face structure adaptedto be applied against or close to the field admission windows.

[0028] Typically, the radio frequency power supply means deliver powerat a frequency around 10 kHz to 100 MHz, preferably at a frequency of13.56 MHz.

[0029] According to another embodiment of the invention, the pluralityof ionisation energy sources are disposed at each side of the substrateaccording to an array of two dimensions.

BRIEF DESCRIPTION OF THE DRAWINGS

[0030] The invention and its advantages will be better understood fromthe following description, given as non-limiting examples, of preferredembodiments with reference to the appended drawings, in which:

[0031]FIG. 1 is a schematic cross-sectional view of an apparatus forplasma treatment according to a first embodiment of the invention;

[0032]FIG. 2 is schematic perspective view of a coil arrangementaccording to an embodiment of the invention;

[0033]FIG. 3 is schematic perspective view of an apparatus for plasmatreatment according to a second embodiment of the invention;

[0034]FIG. 4 is a perspective view of two substrates examples; and

[0035]FIG. 5 is a schematic view of a conventional apparatus for plasmasubstrate treatment;

DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0036] The method and apparatus for plasma treatment of a non-conductivehollow substrate according to the present invention will be described inrelation with a first embodiment illustrated in FIG. 1. A tube 1 havinga length L and a diameter a is connected at one extremity to a processgas source 2 through a gas flow controller 3. The process gas suppliedfrom the source 2 contains a precursor, such as acrylic acid, in orderto create plasma. The quantity of precursor supplied to the internalcavity of the tube is controlled by the gas flow controller 3 which setsthe kinetic of the gas injected in the tube. The opposite extremity ofthe tube 1 is in communication with a device 4 connected to a vacuumpump 5.

[0037] Four ionisation energy sources 7 to 10 are disposed adjacent toeach other along the substrate length L. The ionisation energy sources,which will be referred hereinafter as plasma sources, each comprises afirst and second electrodes 7 a, 7 b (respectively 8 a, 8 b; 9 a, 9 b;and 10 a, 10 b) facing each other with the substrate therebetween. Theelectrodes of each plasma source have dimensions adapted to produce anelectric field therebetween covering at least the diameter or the widthof the tube.

[0038] Although FIG. 1 shows an embodiment comprising a set of fourplasma sources, the number of plasma sources is not limited to thisvalue. The apparatus of the present invention may comprise more or lessplasma sources depending on the dimensions of the substrate to betreated.

[0039] Moreover, according to the present invention, the plasma sourcesare of a size which ensures generating a uniform electric field whilebeing suitably disposed along the substrate to be treated. The sourceare controlled by a processing means so that the motion of either thetube or a single source, carried out in the prior art, may be recreatedfrom a set of static plasma sources, thus avoiding the drawbacks of theprior art solutions.

[0040] The plasma sources 7 to 10 are connected to a radio frequency(RF) power source 6 through corresponding supply lines 17 to 20. Thesupply lines 17 to 20 each comprise a switch SW. The switches SW1 to SW4are independently controlled by a processing device 11 such as a microcontroller through corresponding output terminals S1 to S4.

[0041] The plasma source can be either a capacitively coupled plasmasource or an inductively coupled plasma source. In FIG. 1, for example,the sources illustrated are of a capacitively coupled plasma sourcetype. An electric field 12 is created between the electrodes 8 a and 8 bof the source 8 by reactance coupling when the electrodes are powered bythe RF power supply 6.

[0042] The four ionisation plasma sources 7 to 10, which can be acapacitively coupled plasma source or an inductively coupled plasmasource, define four plasma creation zones P1 to P4 delimited by thespecific electric field produced from each source. Accordingly, theplasma creation can be controlled for each plasma creation zone P1 to P4through the processing means 11 which controls the open/close state ofthe switches SW1 to SW4 provided in the supply lines 17 to 20 of thesources 7 to 10. Each plasma source can be powered by a common RF powersource or by a separate source.

[0043] The plasma is thus created along the tube by the set of sources 7to 10 sequentially powered. A main advantage of this configuration isthe possibility to regulate the “plasma source motion” with requiredvelocity, frequency and direction.

[0044] Indeed, since the powering of the source can be independentlyinitiated by the processing means, the velocity of the plasma sourcemotion along the tube 1 is regulated by the frequency at which theswitches are sequentially closed. The direction of the plasma sourcemotion is determined by the order according to which the switches areclosed under the control of the processing means. Furthermore, in thesame way, the frequency of the plasma source motion is determined by thenumber of times the processing means causes the sources to be powered.In view of this, the velocity, the direction and/or the frequency of theplasma source motion can be set to a fixed or variable value dependingon the sequence programmed in the processing means.

[0045] According to an implementation of the method plasma treatment ofthe invention, the process gas is permanently flowed in the substrate ata constant precursor rate while the plasma sources are sequentiallypowered. In this case, a fixed programmed sequence of source poweringmay be suitable.

[0046] Nevertheless, the sequence of source powering can be programmedin such a way that the frequency, the velocity and/or the direction ofthe plasma source motion can be controlled according to the process gasflow injected inside the substrate. The process gas flow may bemonitored by the processing means 11 which receives a gas flow valuesignal GFV from the gas flow controller 3. Accordingly, if the processgas is not constantly flowed in the substrate, the processing means isable to correct this irregularity by modulating one or more parameterswith regards to the control of the source motion accordingly. Thisprovides means for ensuring the plasma to have a local density uniformall along the substrate.

[0047] Alternatively, the plasma creation inside the substrate can beobtained in a pulsed way. In order to do this, the RF power source 6 isof a pulse generator type. The same applies when each plasma source ispowered by a separate source which is, in this case, of a pulsegenerator type.

[0048] Furthermore, the gas flow can be also pulsed by the gas flowcontroller 3. When the process gas containing the precursor is notpermanently flowed in the substrate, it must be renewed at least betweeneach powering sequence of the sources in order to maintain a constantprecursor concentration in front of the sources when plasma is created.Therefore, if the process gas is supplied in the substrate in a pulsedway, the gas flow controller 3 can be slaved to the powering sequencesof the plasma sources so that the injection of the process gas issynchronized with the powering of each plasma source. To this end, theprocessing means 11 has a control_output terminal Spc through which acontrol signal is sent to the gas flow controller 3. The output terminalSpc may also be used for commanded the flowing of process gas accordingto a specific program loaded in the processing means 11.

[0049] In view of the above, a pulsed energy source can be implementedwith or without a pulsed gas flow while, in the same way, a pulsed gasflow can be implemented with or without pulsed energy source.

[0050] The plasma can be also created inside the substrate from sourcesof an inductively coupled plasma type. In this case, the plasma sourcesare comprised of two coil arrangements which can be disposed in thevicinity of the substrate substantially in the same configuration as thepair of electrodes illustrated in FIG. 1.

[0051] An embodiment of one of two coil arrangements, which are similar,is illustrated in FIG. 2. The arrangement 7 a′ comprises an inductor 71disposed according to a serpentine form in such a way that the inductorpresents a series of opened linked loops.

[0052] In another embodiment, the arrangement can comprise a series ofsuperimposed linked loops formed by a single inductor. Such anarrangement allows the inductive energy produced by the inductor to beincreased.

[0053] The coil arrangements in the present invention are not limited tothe two above examples and a man skilled in the art could obviouslyimagine various embodiments for the coil arrangement without anydifficulties.

[0054] The inductor may be associated with a magnetic core in order toincrease and homogenize the magnetic field produced by the inductor.This technical aspect of such an association as also its variousembodiments have already been described in detail in European PatentApplication EP 0 908 923. Referring to FIG. 2, a magnetic core 72includes a pole face structure 73 to ensure that the magnetic fieldminimizes the “dead area” at the intervals between the loops formed bythe inductor. Accordingly, the combination of the magnetic core and theinductor form a coil arrangement which allows an homogenized magneticflux all over the area of the substrate which is covered by the sourceconstituted by two coil arrangements. The inductor 71 is comprised in alower part of the magnetic cores 72 respectively so as to be close tothe substrate to be treated. However, according to the nature of thematerial constituting the magnetic core or the magnetic flux expected,the inductor may be located at different positions in the magnetic core.The magnetic core may be easily matched to the shape and dimensionsdesired.

[0055] With a plasma source comprising two coil arrangements asdescribed above, a transversal magnetic flux, which is substantiallyperpendicular to a substrate cavity length L, is produced. The coilarrangements are both supplied by a RF power source which generates anelectrical current I flowing in the same direction in both inductors ofthe coil arrangements respectively.

[0056] Accordingly, the magnetic flux is produced transversally andperpendicularly to the substrate in a sense determined by the directionof the current flowing in the coils arrangements. As the substrate isnon-conductive, the magnetic flux generates an electric field which isproduced in the substrate plan perpendicularly to the direction of themagnetic flux.

[0057] As the magnetic flux is perpendicular and transverse to thecavity length of the substrate, the electric field circles in a loop allover the substrate plan. Accordingly, the path for accelerating theelectrons is longer and an efficient plasma creation can therefore beobtained.

[0058] As a result, the electrical flux is created in the whole areacovered by the source which ionises the process gas in the correspondingsubstrate volume. This configuration is particularly suitable for plasmatreatment of thin hollow substrates because of its good efficiencycriterion which is, for a transversal flux, about R=0.3, as explained indetail in the European patent application EP 00 400 445 .3.

[0059] Moreover, the propagation of the magnetic field is independent ofthe substrate parts placed in the chamber since they are non-conductive.

[0060]FIG. 3 illustrates a second embodiment of an apparatus for plasmatreatment according to the present invention. In this embodiment, theset of plasma sources is comprised of an array of six plasma sources 107to 112 disposed according two directions. Indeed, the substrate to betreated is a flat box 101 as that represented in FIG. 4. As can be seenfrom FIG. 3, three plasma sources 107 to 109 are disposed adjacent toeach other according to a first row while the sources 110 to 112 arerespectively aligned with the sources 107 to 109 according to a secondrow. The disposition of the plasma sources 107 to 112 according to anarray of two dimensions matches the form of the flat box 101 which,contrary to a tube, presents a width W shown in FIG. 4.

[0061] As shown for the plasma source 107, each source comprises twoparts 107 a and 107 b sandwiching the flat box 101 to be treated. Thetwo parts of each source may be reactance electrodes or, as representedin FIG. 3, two coils arrangements having the structure described above.

[0062] As illustrated only for plasma source 109 in order to simplifythe figure, both coil arrangements 109 a and 109 b are connected to a RFpower source 106 via a switch SW3 which is on/off controlled by theprocessing means 211 through an output terminal S3. Therefore, both coilarrangements of the plasma sources 107 to 112 are sequentially poweredby the source 106 via respective switches SW1 to SW6 which are on/offcontrolled by the processing means 211 through output terminals S1 to S6respectively. As for the embodiment of FIG. 1, each plasma source may bealso powered by a separate RF power source.

[0063] Besides, the coil arrangements of a source are both supplied by asame RF power supply source which generates an electrical current Iflowing in the same direction in both inductors 171 and 172 of the coilarrangements 109 a, 109 b, respectively. The inductors 171 and 172 ofthe coils arrangements 109 a and 109 b may also be independentlysupplied from two separate RF power sources provided that the current inboth inductors flows simultaneously in the same direction in order toprevent a magnetic flux induced from an inductor to be canceled by themagnetic flux induced from the other. In this case, the number ofcontrolled switches together with the number of output terminalsprovided with the processing means 211 will be doubled.

[0064] The coil arrangements may be driven at a frequency of around 10kHz to 100 MHz. For example, the typical operating frequency of 13.56MHz, delivered by the power supply devices commonly used, is sufficientto treat numerous types of thin hollow substrates with an optimumefficiency.

[0065] When a plasma source is powered, a transversal magnetic flux 130,which is substantially perpendicular to a substrate length L is producedby the two coil arrangements of the source. Accordingly, the magneticflux 130 is produced transversally and perpendicularly to the substrate101 in a sense determined by the direction of the current flowing in thecoils arrangements. As the substrate 101 is non-conductive, the magneticflux 130 generates an electric field 131 which is produced in thesubstrate plan perpendicularly to the direction of the magnetic flux130.

[0066] The apparatus comprises a classical plasma chamber 102 in which aplasma processing can be implemented. The chamber 102 includes a sealedarea which can be evacuated and controlled in pressure by evacuatingmeans such as those shown in FIG. 1. The chamber is filled with aprocess gas via a process gas source and a gas flow controller (notshown). As the substrate is included in the sealed area of the chamber102, the process gas can be ionised inside and/or outside the substrateallowing plasma creation inside and/or outside the substrate.

[0067] The plasma chamber further comprises a first and a second fieldadmission windows 102a and 102b made of quartz or other dielectricmaterial such as to allow an energy field to enter inside the chamber byinductive coupling and thereby create or sustain the required plasmaprocessing conditions. The space defined between the two windowssubstantially corresponds to the thickness dimension of the plasmachamber volume occupied by the flat box 101. The form and the dimensionsof the plasma chamber and so the field admission windows depend on theform and the size of the substrate to be treated. For example, the fieldadmission windows have to cover at least the whole widest face of aparallelepipedic hollow substrate or the cylindrical part of a tubularsubstrate.

[0068] As for the first apparatus embodiment described in relation toFIG. 1, the processing means 211 are specifically programmed so as tocontrol sequentially the on/off state of the switches SW1 to SW6, thusdetermining the direction, the velocity and/or the frequency of theplasma source all over the substrate. The difference with the firstembodiment is that the plasma source motion can be controlled withrespect to two dimensions. The gas flow inside the substrate may be alsoslaved to the processing means 211 through the output terminal Spc.

1. Method for plasma treatment of a hollow substrate (1; 10), comprisingthe steps of: a) placing a plurality of ionisation energy sources (7-10;107-112) all along the part of the substrate to be treated, b) injectinga process gas inside the substrate, said gas containing a precursor forplasma creation, and c) maintaining pressure inside the tube within apredetermined range, characterised by comprising the further step of: d)powering from a single radio frequency power source (6; 106) theionisation energy sources, in sequence, for selectively creating plasmainside the substrate at a location corresponding to the respectivesource powered, said step b) of injecting the process gas being repeatedat least before the powering of each ionisation energy source, saidsingle radio frequency power source delivering power at a frequencyaround 10 kHz to 100 MHz.
 2. Method for plasma treatment according toclaim 1, characterised in that said step b) is commanded in accordancewith the sequences of powering the ionisation energy sources.
 3. Methodfor plasma treatment according to claim 1, characterised in that in saidstep b) of injecting a process gas inside the substrate, the process gasis continuously injected inside the substrate at a constant precursorrate.
 4. Method for plasma treatment according to any one of claims 1 to3, characterised in that the plurality of ionisation energy sources arecapacitively coupled plasma sources (7-10).
 5. Method for plasmatreatment according to any one of claims 1 to 3, characterised in thatthe plurality of ionisation energy sources are inductively coupledplasma sources (107-112).
 6. Method for plasma treatment according toany one of claims 1 to 5, characterised in that the ionisation energysources are powered in a pulsed fashion.
 7. Method for plasma treatmentaccording to any one of claims 1 to 6, characterised in that thesubstrate (1; 101) is a hollow substrate with a large aspect ratio(L/a).
 8. Method for plasma treatment according to any one of claims 1to 7, characterised in that, in said step a), the plurality ofionisation energy sources (107-112) are placed according to an array oftwo dimensions.
 9. Apparatus for plasma treatment of a non-conductivehollow substrate (1; 101), comprising generation means for generating aplasma in the substrate, said generation means comprising a plurality ofionisation energy sources (7-10; 107-112) disposed adjacent to eachother all along the part of the substrate to be treated, characterisedin that said apparatus further comprises a processing means (11; 211)for sequentially powering the plurality of ionisation energy sourcesfrom a single radio frequency power supply means (6; 106), said singleradio frequency power source delivering power at a frequency around 10kHz to 100 MHz
 10. Apparatus according to claim 9, characterised in thatthe radio frequency power supply means is of a pulse generator type forpowering the ionisation energy sources in a pulsed fashion. 11.Apparatus according to claims 9 or 10, characterised In that theprocessing means comprises output means (Spc) for commanding a gas flowcontroller (3) in accordance with the sequences of powering theionisation energy sources.
 12. Apparatus according to any one of claims9 to 11, characterised in that the plurality of ionisation energysources are capacitively coupled plasma sources (7-10).
 13. Apparatusaccording to any one of claims 9 to 11, characterised In that theplurality of ionisation energy sources are inductively coupled plasmasources (107-112).
 14. Apparatus according to claim 13, characterised inthat each ionisation energy source (109) comprises electromagnetic means(109 a; 109 b) for producing through the substrate (101) a magnetic flux(130) perpendicular to a direction of a substrate length (L). 15.Apparatus according to claim 14, characterised in that it furthercomprises a plasma chamber (102) provided with two oppositely facingfield admission windows (102 a, 102 b) and as electromagnetic means (109a; 109 b), first and second opposite coil arrangements located on anouter surface of the first and second windows respectively, the firstand second coil arrangements being connected to power supply line (119)such that a current (I) of a same direction flows simultaneously in thefirst and second coil arrangements.
 16. Apparatus according to claim 15,characterised in that said first and second coil arrangements compriseseach an inductor (71) having a serpentine form.
 17. Apparatus accordingto claim 16, characterised in that said first and second coilarrangements further comprises a magnetic core (72) associated with theInductors of said coil arrangements, the magnetic core presenting a poleface structure adapted to be applied against or close to the fieldadmission windows.
 18. Apparatus according to any one of claims 9 to 17,characterised in that said plurality of ionisation energy sources aredisposed at each side of the substrate (101) according to an array oftwo dimensions.